XB-48

Martin's six-jet XB-48 was ordered in 1944 as part of a design competition for a postwar jet bomber. An odd mixture of the conventional and the innovative, it lost out to Boeing's swept-wing B-47 and was destined only to become one of aviation's brief oddities. It pioneered the use of tandem main landing gear, which lived on in other designs. Three General Electric J35-A-5 engines were mounted in a single housing beneath each wing, creating a pair of tunnels for airflow. Air passing through was supposed to help cool the engines and to boost the plane's airspeed by means of a venturi effect. This feature, however, proved to be overly optimistic, leading a test pilot to report that he could almost see the air piling up ahead of each wing in flight.